1. Field of the Invention
This invention relates generally to underwater repair apparatus and methods, and more particularly to a method and apparatus for repairing synthetic liners of hazardous waste pits and ponds.
2. Brief Description of the Prior Art
The federal Environmental Protection Agency (EPA) and various state environmental agencies have mandated certain containment and emission requirements for the containment of "hazardous products". The term "hazardous" may refer to a cancer causing product, a poison, or even salt water (brine).
A common state of the art system for containment of restricted liquids utilizes synthetic plastic liners placed as an impermeable membrane over an excavated earthen structure to form a holding pond or pit. The plastic liner may be placed over the earth or a layer of concrete lining the excavation. The assumption is that the synthetic liner will not leak and the fluid will be contained. Often the lined pond or pit is integrated into a system where it is impractical to remove the hazardous liquid to repair the liner in the event of failure. The present invention addresses the problem of repairing such a pond liner in the event of failure of the liner.
There are several patents which disclose apparatus and methods for isolating one section of water from another.
Robinson, U.S. Pat. No. 294,078 discloses a caisson used for casting a concrete pier.
Rebikoff, U.S. Pat. No. 3,380,256 discloses an open top caisson which is sunk into water with the top extending above the surface of the water. The water is then pumped out of the caisson so that a drilling rig can be installed on the bed of the body of water.
Preus, U.S. Pat. No. 4,100,746 discloses an aquatic sports area with boundaries divided by skirts of waterproof sheet material extending from the surface to the bottom to protect the swimming areas.
Salisbury, U.S. Pat. No. 3,078,472 discloses a floating swimming pool which protects swimmers from hazards which has floating edges and a plastic bottom. The entire structure is floated on a body of water and is filled with clean fresh water.
Williamson, U.S. Pat. No. 1,017,486 discloses a diving apparatus with a bell or caisson which is submerged to the bottom of a body of water and is connected by a flexible tubing to a vessel on the surface.
Blanc, U.S. Pat. No. 4,724,790 discloses a submersible diving bell which can be pumped free of water and secured to the bottom of a body of water.
Leary, U.S. Pat. No. 4,362,437 discloses an apparatus for working on a submerged surface such as the hull of a ship. The apparatus includes a liquid type enclosure with an arrangement for the hands of the worker to extend into the enclosure for working in a water-free environment.
The present invention is distinguished over the prior art in general, and these patents in particular by a working chamber which is placed in a lined pond containing a body of contaminated water and filled with clean water to safely isolate divers while they repair damaged areas of the liner. The chamber is an open ended housing having a side wall formed of water impervious material configured to surround the area of liner damage and has a height greater than the depth of the body of water at the repair site. Buoyancy tanks on the housing allow the housing to float in a stable upright position above the repair site and are filled with clean water to sink the housing to rest its bottom end on the liner at the bottom of the body of water. A deformable seal on the bottom end the housing engages the liner surface surrounding the area of liner damage and is filled with water to forming a substantial water sealing relation therewith but with controlled leakage. Clean water is conducted into the chamber interior at a predetermined rate to displace contaminated water inside the chamber. A pump may also be utilized to remove contaminated water from the interior of the chamber. The inlet rate and leakage or removal rate are controlled to provide a column of continuous clean water within the chamber sufficiently safe for human divers to enter the chamber and repair the damaged liner. After the repair, the buoyancy tanks and bottom seal are filled with air and the chamber may be floated to another location or removed.